I've got a Trane XV-80 furnace that just tonight quit.
When starting the ignitor /sometimes/ glows but most of the time does
not...and either way the furnace does not light.
I can light it manually with a match and it will run normally.
The ignigtor appears to be OK...no breaks and the resistance is 130 ohms
What voltage do they operate at and is it AC or DC?
Looks like it must be the controller itself and I know that is going to
The ignitor is maybe 8 years old and I took it out and it looks good...
When I turn the furnace on, at the time the ignitor should be glowing
I'm only getting 4 vac at the leads which I know is too low to make it glow.
My guess however that it needs more than 24 volts as I applied 24 volts
to it and it only got very slightly warm
What little I know of furnace igniters, typically
Some units, they detect the amperage of the
igniter, won't open the gas valve if it's
too high or low. You mention match light,
so that's not an issue.
Most trouble part of a furnace is HSI and flame sensor. HSI needs
replacing, flame sensor needs cleaning. HSI is like ~40.00 or so.
I'd just put in a new one and see. I always keep spare HSI, one at home
abd one at cabin. HSI is like big filament in a light bulb. With
age it won't produce high temp. It has to glow real bright red when it
is on. Worth checking loose connector too. You can tighten the connector
Yep went through everything...
the controller does not supply voltage to the ignitor (except if furnace
is left off for a few hours, then it sometimes works)
Don't want to risk repairing the control board, this being winter...
as the furnace does work now if I light it manually.
Local supplier does not have the control module and it would be quite
expensive. ($470 )
Since I was going to replace this 23 year old furnace this year anyway,
might as well do it now.
Many folks here recommended Goodman, so I am having the local deal stop
by and estimate the job in about 4 hours.
It it costs no more than two toilets I'll get it done.
(This summer a plumber told me it would be $2000 to replace a toilet
that I replaced myself for $80)
On Thursday, January 22, 2015 at 10:12:45 AM UTC-5, philo wrote:
I replaced my old Ruud with a new Rheem. Very happy with both, they
are made by the same company. The Ruud went 27 years, only needed to
add a hard-start kit to the AC. Rheem's been in 3 years now, 93%,
two stage, variable speed blower. Really surprised at the fuel savings,
probably 40%+. I was expecting a decent improvement, but that was
more than I hoped for. I'm really a fan of the two stage concept too.
At full output, I can raise the temp 6F an hour. That lets me get
the house back up quickly after being away. It runs at low stage when
maintaining the temp, ie most of the time. Without two stage if you
want a bigger furnace to be able to heat quickly, then it's not going
to run as much as it should to move air around, etc when it's just
I've had good experiences with Goodman. Simple,
reasonably well made, and they use common parts.
Unlike the proprietary Trane odd one off parts.
Christopher A. Young
learn more about Jesus
Check that control board for dust/dirt , at the low voltage signal levels
they work at it's possible there's a short circuit - especially if there's
any condensaton/moisture present . Also possible if they used no-lead solder
that there are tin whiskers shorting something out . Also pull and replace
any signal-level control wiring plugs , sometimes a layer of oxidation can
kill the signal . Had exactly that scenario happen several years ago with a
I PM my furnace every year and the control board is clean and dry.
The leads are pushed properly but I will double check,
The controller is sealed and solid state so it does not look like there
is a relay that I could replace myself.
The controller is a CNT1523 and I see them on-line for $500
Thanks for the help...looks like I'm getting somewhere.
I took every single wire off and removed the control unit...put it on my
bench and opened it up...It's like new inside clean and shiny.
I then just put everything back together and made are all connections
were good...and I'll be darned the furnace started right up.
None of the wires or push on connectors looked burned...so it very well
may have been tarnish...
I worked with push-on connectors for my job and though it was not
common, I had seen that before.
If it stays working for the next few days hopefully it will stay that
way for a while...
but I will be seriously thinking of replacing the furnace...
but don't want to have it done in an emergency.
Must have just been a fluke
the furnace ignitor did not work a 2nd time
Since I can light it manually and the temp here is moderate...even
though it looks like new furnace time...I at least won't have to make it
an emergency call
plus...we have a 220v baseboard heater that can keep the upstairs quite
warm even without a furnace .
That photo was very small and it was hard to make out...but the board
does have a lot of relays on it and...yes I could figure out which one
is for the ignitor and change it...
Were it summer now, I'd do it
However since the furnace is semi working now...I'm not sure I want to
take the chance of taking it out completely
Plus I found out that if I turn off the input power for a few hours,
then turn it back on, it will start normally without me having to light it.
I looked up the specs on the exact ignitor I have and the cold
resistance is approx normal
Plus it /does? work when there is 115v on it.
The problem is that the output is only usually 4 volts...
but if I turn the furnace off for a few hours and turn it back on...the
first time it does supply the right voltage.
Anyway this was the year I was going to replace the furnace anyway and I
now have a contractor coming out to give me an estimate on a new one.
I got a look at the 2nd image you posted and it's not the same control
that I have...but it's somewhat similar.
There is a Trane parts depot here in town and they do not have a control
in stock, they'd have to order it
Thank you very much for the great help
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